A – Z of Illnesses & Conditions

Hives: Hives are swollen, red or pink bumps or patches that usually appear suddenly on the skin. Itching is the most common symptom associated with hives, although some people report that hives cause a stinging or burning sensation. Hives are a very common reaction to all kinds of stimuli. While an allergic reaction can be a cause of hives, in the majority of outbreaks, the exact cause of hives is not known.

Hives occur when histamines are released by specialized cells known as mast cells. It is true that allergic reactions ultimately lead to the release of histamine but other circumstances can result in the release of histamine, causing an outbreak of hives. Histamines cause blood vessels to leak fluid into the nearby tissues. In the skin, small areas of swelling develop as a result of capillary (the smallest blood vessels) leakage.

In addition to allergic reactions to medications, foods or other substances, hives may be triggered by direct physical stimulation such as temperature extremes, water, sun, and physical exercise. Having a viral infection can also cause an outbreak of hives. Stress and nervousness have been associated with hives outbreaks.

Your doctor will usually be able to diagnose your hives by examining the rash on your skin. If you have persistent Hives, you may be referred to a skin specialist (dermatologist).